Frequências de pastejo e níveis de adubação nitrogenada como estratégias de manejo sustentável do capim-tamani

Abstract

Monteiro, G.O.A. Grazing frequencies and nitrogen fertilization levels as sustainable management strategies for tamani grass. Dissertation (Masters) - Faculty of Veterinary Medicine and Animal Science, Federal University of Mato Grosso do Sul, Campo Grande, MS, 2022.

This study evaluated the effect of grazing frequencies and nitrogen (N) rates on the morphogenic, structural and productive characteristics of tamani grass. The experimental design was in randomized blocks, factorial scheme with two grazing frequencies, represented by the levels of light interception (LI), 90 and 95%, and two doses of N (80 and 240 kg/ha/year), the technique grazing was intermittent stocking. The variables evaluated were: LI, canopy height, tiller population density (TPD), tillering dynamics, morphogenesis, forage mass, forage accumulation and morphological components. There was an interaction between LI levels and N doses (p<0.05) for grazing cicle number, forage mass (FM) in pre-grazing, forage accumulation (FA), leaf appearance rate (LAR) and leaf elongation rate (LER). The treatment with 95% IL and 240 kg/ha/year of N obtained the highest yields with 4870.9 kg/ha of FM and 2219.7 kg/ha of FA. The treatment of 90% of IL 240 kg/ha/year of N obtained higher LAR and LER, with 0.08 leaves/tiller/day and 1.88 cm/tiller/day, respectively. There was an effect of LI levels (p<0.05) for height, interval between grazing (IBG), TPD and tiller survival rate (TSR). Higher values of height (39.3 cm), IBG (94.6 days) and TSR (0.996 tillers/day) were observed at the level of 95% of LI and higher TPD (1229.6 tillers/m2) at the level of 90 % of IL. Nitrogen fertilization influenced (p<0.05) the stem elongation rate (SER), tiller appearance rate (TAR) and TPD. Pastures that received the highest dose had higher TPD (1264.2 tillers/m2), SER (-0.03 cm tiller/day) and TAR (0.015 tillers/day). Managing tamani grass pastures with a grazing frequency of 95% LI and 240 kg/ha/year N allows for higher forage productivity and greater persistence.

Keywords: canopy structure, grazing management, nitrogen, Panicum.